1. Field of the Invention
The present invention relates to a continuous variable valve lift (CVVL) device in which a valve has simultaneously variable lift time and distance depending on the low-speed/high-speed operating range of an engine and, more particularly, to a CVVL device which can be mounted on a CCVL-device-free engine, i.e. a non-CVVL engine, without increasing a gap between a drive cam and a rocker roller.
2. Description of Related Art
As for an engine, a camshaft is rotated by a rotating force transmitted from a crank shaft, and an intake valve and an exhaust valve are reciprocated up and down with regular timing by cams of the camshaft. Thereby, intake air is supplied to a combustion chamber, and combustion gas is exhausted. In this process, a fuel-air mixture is compressed and exploded to generate power.
At this time, a device that can continuously vary the lift distance of a valve according to an operating speed of the engine is called a continuous variable valve lift (CVVL) device.
Hereinafter, a conventional CVVL device will be described in detail with reference to the attached drawings.
FIG. 1 is a side view illustrating the configuration of a conventional continuous variable valve lift (CVVL) device.
As illustrated in FIG. 1, the conventional CVVL device is a device that varies the pivoting angle of a rocker arm 30 depending on various conditions such as an engine speed when the rocker arm 30 is pivoted by rotation of a drive cam 20 coupled to a camshaft 10, and is mounted between the drive cam 20 and the rocker arm 30.
More specifically, the conventional CVVL device includes a first gear 50, a second gear 60, a rocking cam 70 pivoting around a control shaft 72 and pressing a rocker roller 32 of the rocker arm 30 according to a pivoting angle, and a rocking link 80 mounted between the drive cam 20 and the rocking arm 70 and pivoting the rocking cam 70 by means of rotation of the drive cam 20.
The rocking link 80 is hinged to the second gear 60 by a connection pin 82 at one end thereof, and is provided with a rocking roller 84 contacting a top face of the rocking cam 70 at the other end thereof. At this time, the first gear 50 and the second gear 60 serve to set at which portion of the top face of the rocking cam 70 the rocking roller 84 is located. The first gear 50 is configured to be able to be rotated around the control shaft 72, and the second gear 60 is configured to be able to be rotated around the camshaft 10.
Thus, when the rocking roller 84 is located at a right-hand end of the rocking cam 70, namely when the rocking roller 84 is located at a position remote from the pivoting center of the rocking cam 70, the pivoting angle of the rocking cam 70 is increased when the rocking roller 84 moves down by means of the drive cam 20, so that the lift distance of a valve 40 is increased.
In contrast, when the rocking roller 84 is located on a left-hand side of the rocking cam 70, namely when the rocking roller 84 is located at a position adjacent to the pivoting center of the rocking cam 70, the pivoting angle of the rocking cam 70 is decreased when the rocking roller 84 moves down by means of the drive cam 20, so that the lift distance of the valve 40 is decreased.
However, as described above, the conventional CVVL device is configured to be mounted between the drive cam 20 and the rocker arm 30. Thus, in the case in which the conventional CVVL device is to be applied to an engine on which the CCVL device is not mounted, i.e. a non-CVVL engine, positions of the drive cam 20 and the rocker arm 30 must be changed.
Further, if a gap between the drive cam 20 and the rocker arm 30 is increased, the total height of the engine is increased.
In addition, in the case of the conventional CVVL device configured as described above, when the control shaft 72 is pivoted in order to change a position of the rocking roller 84, a rotating force of the control shaft 72 is transmitted to the rocking link 80 via the first and second gears 50 and 60. Here, since the second gear 60 is configured to be pivoted around the camshaft 10, there is a possibility of the camshaft 10 being abnormally operated by friction between the second gear 60 and the camshaft 10.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.